Stator construction for axial flow compressors



Feb. 22, 1955 w. A. LEDwlTH STATOR CONSTRUCTION FOR AXIAL FLOWv COMPRESSORS 2 sners-sneet 1 Filed March 7, 1951 Feb. 22, 1955 w. A. LEDwlTH STATOR CONSTRUCTION FOR AXIAL FLOW COMPRESSORS Filed March 7, 1951 2 Sheets-Sheet 2 [uveizzoI-/f Mali@ f L@ ivi/ii' m y Hilfen/sgg United States Patent O STATOR CONSTRUCTION FOR AXIAL FLOW COMPRESSORS Walter A. Ledwith, Glastonbury, Conn., assiguor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application lVIarch 7, 1951, Serial No. 214,241

3 Claim. (Cl. 230-114) The present invention relates to a stator construction for an axial ow compressor and particularly to an arrangement for bleeding of the compressor in successive sta es.

lgn a compressor having a high capacity, it is frequently necessary, under certain conditions of operation, to provide for bleeding the compressor between the end stages, as, for example, in getting the compressor up to speed or under certain inlet pressure conditions. Effective bleed ing necessitates suiiicient bleed ports to handle a large part of the uid within the compressor at the point at which bleeding takes place. A feature of the present invention is an arrangement for readily and conveniently controlling the escape of air from a large number of bleed holes simultaneously.

ln order that bleeding may be uniform for the entire circumference of the compressor the bleed holes are arranged substantially uniformly in the casing thereby making diticult an arrangement for closing oil. all of these ports simultaneously. A feature of the invention is a double walled compressor casing with the walls spaced apart to provide manifolds communicating with the bleed holes in the inner casing and with large control vents in the outer casing.

Another feature of the invention is an arrangement for assembly of a double walled casing of this character in which the inner casing wall is piloted within the outer wall at spaced points axially of the stator in such a way as to provide the essential manifolds without the necessity for providing additional structure adapted strictly for the purpose of the manifolds.

Other objects and advantages will be apparent from the specification and claims, and'from the accompanying drawings which illustrate an embodiment of the invention.

Fig. 1 is a longitudinal sectional view through the compressor.

Fig. 2 is a fragmentary sectional view substantially o the line 2 2 of Fig. 1.

Fig. 3 is an enlarged fragmentary View of the portion of Fig. l designated approximately by A.

Fig. 4 is an enlarged fragmentary view of the portion of Fig. 1 designated approximately by B.

Fig. 5 is an enlarged fragmentary view of the portion of Fig. 1 designated approximately by C.

Fig. 6 is an enlarged fragmentary view of the portion of Fig. 1 designated approximately by D.

Fig. 7 is an enlarged fragmentary view of the portion of Fig. 1 designated approximately by E.

Fig. 8 is an enlarged fragmentary view of the portion of Fig. l designated approximately by F.

in the arrangement shown, the compressor includes a casing 10 supporting spaced rows 12 of stator vanes which alternate with similarly spaced rows 14 of rotor blades extending radially outward from the rotor 16. The rotor is located centrally within the casing as by bearings 18 and 20. The bearing 18 is supported in a housing 22 carried by the casing 10 through struts 24 extending across the path of air ow through the compressor. The bearing 20 is also supported concentrically of the casing 10 by housing 26.

The rotor construction may be conventional. In the arrangement shown the blades of successive rows 14 are carried by rotor discs 28 which have projecting anges 30 on opposite sides thereof which engage with similar anges on adjacent discs for properly spacing the discs axially. 'Ihe outer edges of the anges 30 may have interengaging face splines 32 which function to pilot the discs for ac 2,702,665 Patented Feb. 22, 1955 curate axial alignment. Each of the bells 34 at opposite ends of the rotor also carries a row of blades, as shown. The assembled rotor may be held together by a centrally located through bolt 36 clamped securely as by means of a nut 38 within one of the end bells. Although the blades are shown as integral with the rotor disc, it will be understood that the blades may be separable therefrom by the usual type of blade fastening.

The casing 10 for the compressor is made up of an outer casing member 40 and an inner casing member 42, which, except at the ends of the casing, are spaced apart to dene manifolds between the two casing parts. The outer casing 40 may be made up of two separate circumferentially continuous casing rings 40a and 40b. Each of the rings 40a and 40b preferably decreases in diameter from one end to the other and also has axially spaced, circumferentially extending, piloting surfaces 46 between its ends by which to position the inner casing accurately within the outer casing. The separate rings 40a and 40b may be bolted together in axial alignment as by bolts 48, Fig. 6.

The inner casing 42 is made up of a plurality of separate rings 50 on which the rows 12 of stator vanes are positioned. In the particular arrangement shown, the left-hand end ring 50a, for example, carries two axially spaced rows of stator vanes as does the second ring 50b. Succeeding rings carry two rows of stator vanes apiece with the exception of ring 50g which carries only one row of vanes. Downstream of the last stator-vane carrying ring 50g is another ring 50h which carries the straightening vanes 52. Each of the rings 50 has a piloting ange at one end which engages with the outer casing and at its opposite end has a device by which to pilot the ring with respect to the adjacent ring. Thus, for example, the upstream edge of the ring 50a has a radially extending ange 54, Fig. 3, which overlies a similar ange 56 on the outer casing and is clamped against relative rotation with respect to the outer casing as by suitable bolts 58. The downstream end of casing ring 50a has a radially extending ange 60, Fig. 4, which has a number of axially extending piloting pins 62 therein to engage with the ange 64 on the upstream end of the adjacent casing ring 50h. The ange 64 has a piloting surface 66 which engages with one of the piloting surfaces 46 on the inner surface of the outer casing. The piloting pins also serve to transmit torque between adjacent rings thereby preventing the rings from turning within the outer casing member.

The downstream end of casing ring 50b is similarly piloted by pins 68, Fig. 5, with respect to the upstream end of the casing ring 50c, the latter having instead of a continuous piloting surface an interrupted flange 70, as best shown in Fig. 2, the latter having a peripheral surface engaging with one of the piloting surfaces 46.

The downstream edge of ring 50c has a peripheral notch 72, Fig. 6, to receive the projecting upper end 74 of the ring 50d. At this point the adjacent rings are merely piloted for axial alignment without a provision for the transfer of torque between adjacent rings. It will be apparent that rings 50a, 50b and 50c are held against relative rotation and are also prevented from turning within the outer casing through the medium of the torque-transfer pins 62 and 68 and the radially extending ange 54. The rings 50d, 50e, 50j, 50g and 50h are also held against turning with respect to one another by torque-transfer and piloting pins 74, Figs. 7 and 8, similar to the pins 62 and 68 and the upstream end of ring 50d has a radially extending ange 7'5, Fig. 6, located between the adjacent ends of the outer casing rings 40a and 40h for taking the torque reaction. The flange 75 is also piloted with respect to the casing, as best shown in Fig. 6 and has a tight engagement therewith as will be apparent. It will be apparent that ring 50e has an interrupted flange 76, Fig. 7, similar to the ilange 70 above descrribed and gie nxt ring 50f has a continuous piloting ange 78,

With the arrangement shown, the inner casing rings 50a, 50b and 50c, which are split, may be assembled over .the rotor, and the outer ring 40a then slid over the inner rings with the assembly held together by the bolts 58. The other inner rings 50d, 50e, 50j, 50g and 50h mav the be positioned over the rotor, and the outer casing ring b slid over them and bolted inplace by the bolts 48. The rings facilitate assembly of pressor by carrying a plurality of rows of varies and also by incorporating the spacing structure that assures the desired axial spacing between adjacent rows of varies:

The inner and outer casings are spaced apart as will b e apparent froir` the drawings such that a manifold 80 i s defined between the inner and outer casing with this manifold extending from the liange 64 of ring 50b to the ange "on the upstream end of the ring 50d. This manifold communicates with a row of bleed ports 82 which are provided in the ring 50c adjacent to one of the rows 12 of stator vanes. These ports are preferably uniforinly spaced circumferentially of the ring 50cand serve to bleed air from the compressor when bleeding is required. t The manifold v is vented through one .or more large openings 84 in the outer casing,- there beingV two of these openings in the arrangement shown, as best seen from Fig. 2. Each of'these openings 84 has a ported cylinder 85 extending outwardly therefrom, and a surrounding valve seat 86 in a position to be engaged by a sliding valve 88 positioned within the ported cylinder. It will be apparent that the valve 88 may be closed by the application of pressure through a duct 92 to the outer end of the cylinder thereby moving the valve 88 inwardly against its seat at the same time closing the pons 94 in the wall of the cylinder. Y c

If the compressor requires additional bleeding adjacent to another compressor stage as, f or example, by the us e of another row of bleed ports 96 in the ring 50d, a manifold 98 may be provided between the ange 75'on the upper end of the ring 50d and the ange 78 on ring 50j. This manifold would be vented as by a valve 100 similar to the valve 88. It is obvious that the pressure for closing either of valve 88 or 100 may be obtained from the compressor at a point downstream of the bleeds.

With the arrangement shown the inner casing rings may be provided with a large number of bleed ports to make sure of adequate and uniform bleeding of the compressor between adjacent stages with the escape of air from these ports controlled through the medium ofv a small number of large dump valves which may be more readily controlled than an arrangement which would be utilized for closing the bleed ports individually.

It is to be understood that the invention is not limited to the specific embodiment lherein illustrated and described, but may be used in other ways without departing from its spirit as delned by the following claims.

I claim:

-1. In a multi-stage compressor, an outer casing having a plurality of axially spaced piloting surfaces on its inner surface, a plurality of vane supporting rings positioned within said casing, said rings being in end-to-end engagement with one another, at least one row of varies being carried by and extending inwardly from each ring, and a radially extending piloting ange on each ring engageable with one of the piloting surfaces on the outer casing, said rings forming an inner casing which is spaced at least in part from said outer casing by said anges, at least one of said rings having a large number of large bleed holes extending in a row around said ring and located between adiac'ent rows of vanes, one of the piloting'ilangeslocated adjacent to said row of bleed holes havinga tight engagement with the outer casing, the next adjacent piloting flange being interrupted to provide for uid tlow past said tianges, the spaces on opposite sides of said next adjacent piloting ange being relatively large to dene a bleed chamber communicating with said r ow of bleed ports and at least one large vent valve in the outer casing communicating with said bleed chamber.

2. In a multi-stage compressor, an outer casing having a plurality of axially spaced piloting surfaces on its inner surface, a plurality of vanes supporting rings positioned the com- 4 within s aid casing, said rings being in end-to-end engagement with one another, at least one row of varies being carried by and extending inwardly from each ring,and a radially extending piloting flange on each ring engageable with one of the piloting surfaces on the outer casing,

said rings forming an inner casing which is spaced at least in part from said outer casing by said anges, at least two of said rings, adjacent to each other, each having a large number of large bleed holes extendingv in a row around said ring and located between adjacent rows of varies, one of the piloting anges being located between the rows of bleed holes and having a tight engagement with the outer casing, the next adjacent piloting surface, a plurality of v ane supporting rings positioned within said casing, said rings being in end-to-end engagement with one another, at least one row of vanes being carried by and extending inwardly from each ring, and a radially extending piloting ange on each ring engageable with one of the piloting surfaces on the outer casing, said rings forming an inner'casing which is spaced at least in part from said outer casing by said flanges, at least two of said rings each having a large number of large bleed holes extending in a row around said ring, eachrow of holes being located between adjacent rows of vanes, said outer casing comprising atleast two separate rings in substantial axial alignment with each other, one of the piloting flanges being located between the rows of bleed holes and extending outwardly between the adjacent ends of the outer casing rings, the latter being secured together to provide a tight engagement with the piloting llange, the next adjacent piloting ange on each side of said one piloting ange being interrupted to provide for tluid tlow past said anges, the spaces between the outer and inner casings on opposite sides of each ot'k said next adjacent piloting lianges being relatively large thereby to define bleed chambers one of which is located on each side of said one piloting ange, with one chamber communieating with each row of bleed ports, and at least two large vent valves in the outer casing with one valve communieating with each of said bleed chambers.

References Cited in the le of kthis patent UNITED SIATES PATENTS 1,399,215 Kerr Dec. 6, 1921 1,647,178 Herr a Nov. l, 1927 2,243,467 Iendrassik May 27, 1941 2,404,275 Clark et al. uly 16, 1946 2,445,661 Constant et al Iuly 20, 1948 2,465,099 Johnson Mar. 22, 1949 2,479,573 Howard Aug. 23, 1949 2,487,842 Whiteman Nov. 15, 1949 2,548,886 Howard Apr. 17, 1951 2,610,786 Howard Sept. 16, 1952.

FOREIGN PATENTS 113,789 Sweden Apr. 10, 1945` 296,477 Germany Feb. 9, 1917 493,175 France 1919 579,976 Great Britain 1946 600,019 Great Britain Mar. 30, 1948 622,895 Great Britain May 9, 1949 900,371 France 1945 

